The present invention relates to a suspension member attaching structure for an automobile or the like.
A suspension mechanism of an automobile or the like has various suspension members (for example, a suspension frame). Conventionally, such a suspension member is attached to a vehicle body structure member (side member, cross member, sub-frame, or the like) by using various types of attaching structures.
First, an automotive suspension mechanism will be explained with reference to FIG. 5. In FIG. 5, reference numeral 40 denotes a suspension member. This suspension member 40 is attached to a member on the lower surface of vehicle body floor via a later-described suspension member attaching structure 41.
The suspension member 40, which is made up of various types of suspension arms 42 (a lower arm 42A rotatably supported in a predetermined geometric relationship, a front upper arm 42B, a rear upper arm 42C, and a lateral link 42D), or a front sub-frame (not shown) or the like, gives a predetermined restraining motion to an illustrated road wheel 43. Reference numeral 44 denotes a shock absorber, and 45 denotes a coil spring.
FIGS. 6 and 7 show conventional suspension member attaching structures.
The suspension member attaching structure shown in FIG. 6 has been disclosed in Unexamined Japanese Patent Publication Nos. 10-211887 and 9-132171. According to this structure, a suspension member attaching structure 41 has a cross member 22 whose flange portion 22A is fixed to the lower surface of a vehicle body floor 21 by welding, and a lower reinforcing member 23 is fixed onto the bottom surface of the cross member 22. To the lower reinforcing member 23, a bolt plate 24 having a fitting hole 24A at the center thereof is fixed by welding at the peripheral portion of the bolt plate 24.
A bolt 25 is attached to the bolt plate 24 by fitting a serrated portion 25A of an intermediate portion of the bolt in the fitting hole 24A. To the upper end portion of the bolt 25 is fixed a separate upper pin 30, and the bolt 25 is fixed to an upper reinforcing member 31 by causing the upper pin 30 to pass through a hole 32 in the upper reinforcing member 31 and by arc welding the upper pin 30. A rising portion 33 at the periphery of the upper reinforcing member 31 is fixed to the cross member 22 by spot welding. A projecting portion of the bolt 25 projecting from the cross member 22 is supported on the suspension member 40 via an insulator in which an elastic material 27C is interposed between an inner cylinder 27A and an outer cylinder 27B. A nut 28 is screwed to a screw portion 25D of the bolt 25, by which the inner cylinder 27A of the insulator 27 is fastened and held via a cover member 29.
The suspension member attaching structure shown in FIG. 7 has been disclosed in Unexamined Japanese Patent Publication No. 10-211887. According to this structure, a pin portion 57 is formed integrally at the upper part of a bolt 53. By caulking the pin portion 57 in an insertion hole 56C in an upper reinforcing member 56, the upper part of the bolt 53 is fixed to the upper reinforcing member 56, a collar portion 54 formed at an intermediate portion of the bolt 53 is held between an embossed member 55D and a bottom surface portion 52C of a cross member 52, and further the bolt 53 is fitted in a through hole 55C in a lower reinforcing member 55.
However, for the suspension member attaching structure shown in FIG. 6, the attachment strength of the bolt 25 (suspension member) depends on a serration fit due to the serrated portion 25A of the bolt 25. Therefore, in order to increase the attachment strength, the bolt plate 24 or the lower reinforcing member 23 itself must be made thick or large. Also, because of the construction in which the attachment strength depends on a serration fit due to the serrated portion 25A, in order to increase a resisting force against a thrust-up force applied to the bolt 25, the hardness of the serrated portion 25A of the bolt 25 must be increased to enhance a force for fitting to the bolt plate 24. To increase the hardness of the bolt 25, the bolt must be subjected to special treatment such as thermal refining when the bolt 25 is manufactured, so that the manufacture of the bolt 25 is made troublesome. Further, because of high hardness of bolt, the bolt 25 cannot be welded directly to the upper reinforcing member 31, so that the separate upper pin 30 with relatively low hardness is needed. For this reason, the alignment of the bolt 25 and the upper pin 30 is difficult to do. Also, it is very difficult to obtain a perpendicular accuracy of the bolt 25 with respect to the cross member 22, coupled with the reason that consideration must be given to the fact that the bolt 25 is fitted so as to be undesirably tilted with respect to the bolt plate 24 because of fitting using the serrated portion 25A.
Also, for the suspension member attaching structure shown in FIG. 7, because the bolt 53 is fixed to the upper reinforcing member 56 by caulking, it is very difficult to obtain a perpendicular accuracy of the bolt 53 with respect to the cross member 52, coupled with the reason that consideration must be given to the fact that the bolt 53 is fitted so as to be undesirably tilted with respect to the bolt plate 54 because of the fitting using the serrated portion 53A. Further, because of the configuration such that the bolt plate 54 is fixed by being held between the bottom surface portion 52C of the cross member 52 and the embossed portion 55D of the lower reinforcing member 55, the flatness between the bottom surface portion 52C of the cross member 52 and the bolt plate 54 and between the bolt plate 54 and the embossed portion 55D affects the perpendicular accuracy of the bolt 53 with respect to the cross member 52. Therefore, it is difficult to obtain the perpendicular accuracy of bolt for this reason as well.
Accordingly, an object of the present invention is to provide a suspension member attaching structure in which a resisting force against a thrust-up force applied to a bolt is increased without the increase in hardness of the bolt, and moreover the perpendicular accuracy of bolt is obtained easily.
To achieve the above object, the suspension member attaching structure in accordance with the present invention is configured so that a lower reinforcing member is connected to the upper surface of a bottom portion of a vehicle body structure member by welding, an upper reinforcing member is provided at an intermediate height position of the vehicle body structure member, the upper part of a bolt is fixed directly to the upper reinforcing member by welding such as arc welding, a collar portion formed at an intermediate portion of the bolt is fixed to the lower reinforcing member by welding such as arc welding, and the lower part of the bolt passes through the lower reinforcing member and the bottom portion of the vehicle body structure member and projects from these two members.
According to the above-described configuration, the upper part of bolt is fixed directly to the upper reinforcing member by welding such as arc welding, and the collar portion of bolt is fixed to the lower reinforcing member by welding such as arc welding. As a result, as compared with the conventional configuration using a fitting system using a separate pin or a serrated portion, a resisting force against a thrust-up force applied to the bolt can be increased, and moreover the perpendicular accuracy with respect to the vehicle body structure member can be assured easily.